The present invention relates to a room temperature purification method and to a room temperature regenerable purification system for Nitrous Oxide.
Nitrous oxide has many industrial uses requiring an accurate control of impurity levels within this gas, among the most demanding ones there are semiconductor manufacturing processes such as chemical vapour deposition, selective oxidations such as in display manufacturing, and rapid thermal oxynitridation process for the fabrication of metal oxide semiconductor (MOS) capacitors.
In all these applications, impurities such as H2O, CO2,CO and similar play a detrimental role by degrading and interfering with the characteristics and performance of the device/component wherein N2O is used as process gas.
Among the most critical impurities is CO2, which is not easily and efficiently removed by means of the standard industrial distillation processes, such as the ones described in the European patent application EP 0636576, because of the close value of the condensation temperature of CO2 and N2O. For this reason, separation plants are not suitable to achieve a sufficient level of purity for electronic grade N2O, as regards the CO2 content.
In the context of the industrial use of purified Nitrous Oxide, it is important to have a purifier capable of operating normally at room temperature and also of being regenerated, in order to increase the purifier lifetime.
For a N2O purification process, it is of importance to develop a solution capable of achieving a sufficiently high capacity in order to avoid the use of an excessive amount of purifier media, which would be disadvantageous because of both the associated costs and the volume taken by a purifying system using such media. In addition, a high capacity avoids the need to recur to the regeneration process with an excessive frequency. A suitable target capacity for the purifier material is 0.5 l/l or higher. The liter/liter unit indicates the capability of a given volume (expressed in liters) of the purifier media to remove a volume of gas impurities expressed in standard liters (measured at atmospheric pressure and 0° C.).
Nitrous Oxide purification systems of the prior art generally require cooling apparatus in order to reach levels of efficiency, such as that described in U.S. Pat. No. 7,314,506, comprising cryogenic purification of various gaseous streams, including nitrous oxide, with different materials. Cooling apparatus add cost and complexity to such systems.
These and other limitations of the prior art will become apparent to those of skill in the art upon a reading of the following descriptions and a study of the several figures of the drawing.